Hello:

I am having difficulty with this question:

Assume that, on average, healthy young adults dream 90 minutes each night, as inferred from a number of measures, including rapid eye movement (REM) sleep. An investigator wishes to determine whether drinking coffee just before going to sleep affects the amount of dream time. After drinking a standard amount of coffee, dream time is monitored for each of 28 healthy young adults in a random sample. Results show a sample mean, X, of 88 minutes and a sample standard deviation, s, of 9 minutes.

(a) Use t to test the null hypothesis at the .05 level of significance

(b) If appropriate (because the null hypothesis has been rejected), construct a 95 per-cent confidence interval and interpret this interval

This is what I calculated, but I don't believe it is correct:

Ho: mu=90

H1: mu90

Our one sample t-test statistic is t=88-90/(9/28)=2/1.701=- 1.175

28-1=27 e. p-value=P(t> -1.1759)=0.12495 p=2 *0.12495=0.2499 p-

value=0.2499

The null hypothesis has not been rejected, so there is no need to construct a 95% confidence interval.

Thank you for your help!